The invention relates to an apparatus and method for depositing a uniform coating on a surface of a substrate. More particularly, the invention relates to a method and apparatus for depositing a uniform coating on a surface using multiple plasma sources. Even more particularly, the invention relates to a method and apparatus for depositing a uniform coating on a surface of a substrate using multiple expanding thermal plasma sources.
Plasma sources are capable of depositing a large variety of coatings, such as transparent abrasion resistant coatings, transparent UV-filtering coatings, and multi-layer coating packages on a substrate at a high deposition rate. Individual plasma sources, such as expanding thermal plasma (also referred to hereinafter as xe2x80x9cETPxe2x80x9d) sources, can be used to uniformly coat areas having a diameter in the range of about 10-15 cm.
Arrays of multiple plasma sources may be used to coat larger substrate areas. Such large area coating work typically deals with depositing a coating on macroscopically flat surfaces. The substrate can be coated by translating it in a back and forth, up and down patternxe2x80x94or xe2x80x9cscannedxe2x80x9dxe2x80x94in front of an array of multiple plasma sources. Deposition precursors are usually provided to the multiple plasma sources at the same rate. In this situation it is possible to fabricate large area, uniform coatings. To achieve a uniform coating on a planar surface, the multiple plasma sources may be spaced in a two-dimensional pattern, such as a linear or zigzag array.
When an array of plasma sources is used to coat a large non-planar surface, however, coating uniformity is adversely affected by the dependence of the coating rate upon variations in the source-to-substratexe2x80x94or workingxe2x80x94distance. Thus, those areas on the substrate that are located further away from the plasma source array are coated at a lower rate. The differences in the coating rate across the surface of a substrate results in a non-uniform coating of the substrate.
Arrays of multiple plasma sources are unable to uniformly coat such large non-planar surfaces. Therefore, what is needed is a method and apparatus for uniformly coating a large area surface of a substrate using multiple plasma sources.
The present invention meets these and other needs by providing both a method and apparatus for depositing a uniform coating on a large area, non-planar surface using an array of multiple plasma sources. By locally adjusting the flow of deposition precursor into each of the plasmas generated by the multiple plasma array, the invention compensates for changes in substrate processing conditions due to local variation in the working distance between the plasma source and the substrate surface.
Accordingly, one aspect of the invention is to provide an apparatus for depositing a uniform coating on a surface of a substrate. The apparatus comprises: at least one array of a plurality of plasma sources for generating a plurality of plasmas, wherein each of the plurality of plasma sources includes a cathode, an anode, and an inlet for a non-reactive plasma source gas disposed in a plasma chamber which is maintained at a first predetermined pressure; a deposition chamber for containing the substrate, wherein the deposition chamber is in fluid communication with the plasma chamber, and wherein the deposition chamber is maintained at a second predetermined pressure that is less than the first predetermined pressure; and at least one reactant gas injector disposed in the deposition chamber for providing a differential flow rate of at least one reactant gas into each of the plurality of plasmas.
A second aspect of the invention is to provide a reactant gas injector for injecting at least one reactant gas into a plurality of plasmas generated by an array of a plurality of plasma sources such that a first flow rate of the at least one reactant gas into a first plasma generated by a first plasma source in the array is different from a second flow rate of the at least one reactant gas into a second plasma generated by a second plasma source in the array. The reactant gas injector comprises: at least one reactant gas inlet comprising a tubular-walled structure having an interior space through which the at least one reactant gas is supplied from a reactant gas source; a first plurality of orifices proximate to the first plasma, each of the first plurality of orifices extending through the tubular-walled structure from the interior space to an outer surface of the at least one reactant gas inlet, and a second plurality of orifices proximate to the second plasma, each of the second plurality of orifices extending through the tubular-walled structure from the interior space to an outer surface of the at least one reactant gas inlet. The first plurality of orifices is oriented such that the at least one reactant gas passes from the interior space through the first plurality of orifices and is directed into the first plasma at a first predetermined flow rate and the second plurality of orifices is oriented such that the at least one reactant gas passes from the interior space through the second plurality of orifices and is directed into the second plasma at a second predetermined flow rate.
A third aspect of the invention is to provide an apparatus for depositing a uniform coating on a surface of a substrate. The apparatus comprises: at least one array of a plurality of plasma sources for generating a plurality of plasmas, wherein each of the plurality of plasma sources includes a cathode, an anode, and an inlet for a non-reactive plasma source gas disposed in a plasma chamber which is maintained at a first predetermined pressure; a deposition chamber for containing the substrate, wherein the deposition chamber is in fluid communication with the plasma chamber, and wherein the deposition chamber is maintained at a second predetermined pressure that is less than the first predetermined pressure; and at least one reactant gas injector for injecting at least one reactant gas into the plurality of plasmas such that a first flow rate of the at least one reactant gas into a first plasma generated by a first plasma source in the at least one array is different from a second flow rate of said at least one reactant gas into a second plasma generated by a second plasma source in the at least one array. The at least one reactor injector comprises: at least one reactant gas inlet comprising a tubular-walled structure having an interior space through which the at least one reactant gas is supplied from a reactant gas source; a first plurality of orifices proximate to the first plasma, each of the first plurality of orifices extending through the tubular-walled structure from the interior space to an outer surface of the reactant gas inlet, wherein the first plurality of orifices is oriented such that the at least one reactant gas passes from the interior space through the first plurality of orifices and is directed into said first plasma; and a second plurality of orifices proximate to the second plasma, each of the second plurality of orifices extending through the tubular-walled structure from the interior space to an outer surface of the at least one reactant gas inlet, wherein the second plurality of orifices is oriented such that the at least one reactant gas passes from the interior space through the second plurality of orifices and is directed into the second plasma.
A fourth aspect of the invention is to provide a method of depositing a uniform coating on a surface of a substrate. The method comprises the steps of: providing the substrate having the surface to a deposition chamber; evacuating the deposition chamber to a predetermined deposition pressure; generating a plurality of plasmas from at least one array of a plurality of plasma sources; injecting a reactant gas into each of the plurality of plasmas such that a first flow rate of the at least one reactant gas into a first plasma is different from a second flow rate of the at least one reactant gas into a second plasma; flowing the at least one reactant gas and the plurality of plasmas into the deposition chamber toward the substrate; and reacting the at least one reactant gas with the plurality of plasmas to form the coating on the surface of the substrate.
A fifth aspect of the invention is to provide a method of injecting at least one reactant gas into a plurality of plasmas generated by an array of a plurality of plasma sources such that a first flow rate of the at least one reactant gas into a first plasma is different from a second flow rate of the at least one reactant gas into a second plasma. The method comprises the steps of: supplying the at least one reactant gas from at least one reactant gas source to at least one reactant gas injector; passing the at least one reactant gas through a first plurality of orifices in the at least one reactant gas injector proximate to the first plasma, wherein the first plurality of orifices is oriented such that the at least one reactant gas is directed into the first plasma at a first predetermined flow rate; and passing the at least one reactant gas through a second plurality of orifices in the at least one reactant gas injector proximate to the second plasma, wherein the second plurality of orifices is oriented such that the at least one reactant gas is directed into the second plasma at a second predetermined flow rate.
A sixth aspect of the invention is to provide a non-planar substrate having a uniform coating deposited on a surface, wherein the uniform coating is deposited by: providing the substrate having the surface to a deposition chamber, wherein the deposition chamber is in fluid communication with at least one array of a plurality of plasma sources, wherein at least one of the plurality of plasma sources is an expanding thermal plasma source having a cathode, an anode and an inlet for a non-reactive plasma source gas disposed in a plasma chamber, the plasma chamber being in fluid communication with the deposition chamber; evacuating the deposition chamber to a predetermined deposition pressure and the plasma chamber to a predetermined first pressure, wherein the predetermined deposition pressure is less than the predetermined first pressure; generating a plurality of plasmas in the plurality of plasma sources and flowing the plurality of plasmas into said deposition chamber; injecting at least one reactant gas into each of the plurality of plasmas as the plurality of plasmas flows into the deposition chamber such that a first flow rate of the at least one reactant gas into a first plasma is different from a second flow rate of the at least one reactant gas into a second plasma; flowing the at least one reactant gas and the plurality of plasmas into the deposition chamber toward the substrate; and reacting the at least one reactant gas with each of the plurality of plasmas to form the coating on the surface of the substrate.
These and other aspects, advantages, and salient features of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.